Two male cousins with partial 21-hydroxylase deficiency presented with bilateral testicular masses and infertility. In both cases, the testicular masses, consisting of adrenocorticotropic hormone-dependent pluripotential cells, were thought to play a major etiologic role in infertility. The administration of very small doses of dexamethasone, given at 11:00 P.M., led to the disappearance of the masses and a subsequent return of fertility. Although 21-hydroxylase deficiency is not by itself an uncommon condition, the presentation of testicular masses with subsequent reversible infertility in two family members with this condition has not previously been described.